Black Jupiter 2000 Function generator circuit.

[Mark Hennessy]

This sounds encouraging, as it suggests that the complicated bits are OK. My next move would be to see if there is a signal at the top of the amplitude control (VR17), and that all 3 (triangle, square, sine) are OK. That rules out the switching. Then check the output of the amplifier (junction of R76/77), and if it's OK there, then the output attenuators are likely to be the issue. I guess the amplifier is most likely to be at fault, assuming you've already tried a bit of switch cleaner on all the switches.

Cheers,

Mark